access violation when connecting to server

This is a discussion on access violation when connecting to server within the Networking/Device Communication forums, part of the General Programming Boards category; Hey folks! Here's the compilable code. The line in red is what causes the access violation. Code: #include <winsock2.h> #include ...

  1. #1
    In my head happyclown's Avatar
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    access violation when connecting to server

    Hey folks!

    Here's the compilable code. The line in red is what causes the access violation.

    Code:
    #include <winsock2.h>
    #include <ws2tcpip.h>
    #include <stdio.h>
    #include <stdlib.h>
    
    #define STORAGE_LEN 1000
    #define DEFAULT_PORT "80"
    
    char storage[STORAGE_LEN];
    SOCKET ConnectSocket = INVALID_SOCKET;
    
    void write_to_file(char *storage)
    {
    	FILE *p_openfile = fopen("c:\\programs\\networking\\webpagecontent.txt" , "a+");
    	fprintf(p_openfile, "%s\n", storage);
    	fclose(p_openfile);
    }
    
    int main(int argc, char **argv)
    {
    	WSADATA wsaData;
    	int iResult;
    	struct addrinfo *result = NULL,
    				*ptr = NULL,
    				hints;
    
            // Validate parameters
            if(argc !=2) {
    		printf("usage: %s server-name\n", argv[0]);
    		return 1;
    	}
    
    	// Initialize Winsock
    	iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    	if(iResult != 0) {
    		printf("WSAStartup failed: %d\n", iResult);
    		return 1;
    	}
    
    	sprintf(storage, "WSAStartup = %d\n", iResult);
    	write_to_file(storage);
    
    	ZeroMemory(&hints, sizeof(hints));
    	hints.ai_family = AF_UNSPEC;
    	hints.ai_socktype = SOCK_STREAM;
    	hints.ai_protocol = IPPROTO_TCP;
    
    	// Resolve the server address and port
    	iResult = getaddrinfo(argv[1], DEFAULT_PORT, &hints, &result);
    	if(iResult != 0) {
    		printf("getaddrinfo failed: %d\n", iResult);
    		WSACleanup();
    		return 1;
    	}
    
    	sprintf(storage, "getaddrinfo = %d\n", iResult);
    	write_to_file(storage);
    
    	// Attempt to connect to an address until one succeeds
    	for(ptr = result; ptr != NULL; ptr = ptr->ai_next) {
    		
    		// Create a socket for connecting to the server
    		ConnectSocket = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
    		if(ConnectSocket == INVALID_SOCKET) {
    			printf("Error at socket(): %ld\n", WSAGetLastError());
    			freeaddrinfo(result);
    			WSACleanup();
    			return 1;
    		}
    	}
    
    	sprintf(storage, "socket = %d\n", ConnectSocket);
    	write_to_file(storage);
    
    	// Connect to server
    	iResult = connect(ConnectSocket, ptr->ai_addr, (int)ptr->ai_addrlen);
    	if(iResult == SOCKET_ERROR) {
    		closesocket(ConnectSocket);
    		ConnectSocket = INVALID_SOCKET;
    	}
    
    	freeaddrinfo(result);
    
    	if(ConnectSocket == INVALID_SOCKET) {
    		printf("Unable to connect to the server!\n");
    		return 1;
    	}
    
    	return 0;
    }
    I am still a bit too newbie to know what is the exact problem. Is it because ptr is NULL? Am I supposed to create another struct addrinfo object, and assign ptr to it?

    If I was to write
    Code:
    ptr = result;
    before the line in red, a SOCKET ERROR is the result.

    Thanks in advance.
    Last edited by happyclown; 03-10-2009 at 12:26 AM. Reason: added more code
    OS: Linux Mint 13(Maya) LTS 64 bit.

  2. #2
    In my head happyclown's Avatar
    Join Date
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    Oh, found the problem, I should have closed the for() loop in blue after the connection was made to the server, because ptr is still needed.
    OS: Linux Mint 13(Maya) LTS 64 bit.

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